Correlation between Stokes polarization parameters in emission at 353 GHz and in optical extinction, with the colour in the 2-dimensional histogram representing the density of points. Left: Stokes parameters (Q, U) versus (), yielding an estimate of R_P/p. Right: normalized Stokes parameters (Q/I, U/I) versus (q_V/τ_V, u_V/τ_V), yielding an estimate of R_S/V. The slopes of the correlations are obtained using the Bayesian fitting method of Kelly (2007). The reduced χ², the Pearson correlation coefficient, and the correlation coefficient inferred from the Bayesian method (Kelly 2007) are listed.